Concrete is one of the most important civil engineering materials today. It is characterized by abundant raw material, low price and simple production process as well as high compressive strength, high durability and a wide range of strength grades, so it is widely used in various civil works.
Ordinary concrete is an artificial stone material formed after hardening of the mixture of cement, sand, stone, admixture and water. Sand and stone play a role of framework in concrete and inhibit the contraction of cement. Cement and water form cement paste, which covers the surface of sand and stone and fill the gap between the sand and the stone. Before hardening, cement paste plays a lubricating role and makes concrete mixture have desirable workability. After hardening, it cements the aggregate which plays a role of framework to form a firm body. Ordinary concrete has certain workability, strength, deformation and durability.
However, in the recent years, following the development of the construction industry, the requirements on building materials are getting stricter, particularly on concrete which has the widest use among building materials. Ordinary concrete can no longer meet the requirements of modern buildings on strength and impermeability. Although many kinds of novel concrete keep emerging, their strength and impermeability are still low and need to be improved further.